This invention is generally directed to toner compositions, and more specifically the present invention is directed to toner compositions, including magnetic, black and colored toner compositions with certain charge enhancing additives which impart and/or enhance the positive or negative charging characteristics of these compositions. In one important embodiment of the present invention the charge enhancing additives are formulated by the sorption of known charge additives onto the surface of various flow aid compositions, inclusive of colloidal silicas. Developer compositions with the modified charge enhancing additives of the present invention are useful for enabling the development of electrostatic latent images including color images. More specifically, toner compositions with the aforementioned modified charge enhancing additives are particularly useful in electrostatographic imaging process having incorporated therein a Viton coated fuser roll since these additives do not react substantially with Viton causing undesirable decomposition thereof which adversely effects imaging quality. Also, toner compositions with the treated additives of the present invention possesses improved admix characteristics while enabling colored toner compositions with high concentrations of colorant. Additionally, the modified charge enhancing additives of the present invention are of acceptable fusing performance characteristics in that, for example, these additives have substantially no effect on fusing performance; and further, the additives of the present invention are compatible with, for example, many alternative types of fuser rolls inclusive of Viton, Teflon, fluorinated ethylene polymers, silicones and the like. Moreover, high concentration of known charge enhancing additives can be sorbed onto the flow aid compositions, inclusive of color charge enhancing additives, some of which are highly colored without substantially altering the colors of the toner compositions thereof.
There is disclosed in a number of prior art patents developer compositions with charge enhancing additives. Thus, for example, there are illustrated in U.S. Pat. No. 3,893,935 toner compositions with certain quaternary ammonium salts as charge enhancing additives. Further, in U.S. Pat. No. 2,986,521 reversal developer compsitions comprised of toner resin particles coated with finely divided colloidal silica are illustrated. According to the disclosure of this patent, development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition with a positively charged triboelectric relationship in respect to the colloidal silica. Moreover, toner compositions with sulfate and sulfonate charge enhancing additives are described in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference. Also, U.S. Pat. No. 4,298,517, the disclosure of which is totally incorporated herein by reference, illustrates toner compositions with alkyl pyridinium halide charge enhancing additives.
Other documents disclosing toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014 and 4,394,430. Also of interest are Japanese Patent Abstract Publications Nos. 55079-454; 57129-446; 57079-951; 57078-550; and German DE No. 3208635. Disclosed in the No. '454 abstract is a dry processable electrophotographic developer with a hard powder, such as aluminum oxide which has been previously subjected to surface treatment. The No. '446 document discloses an electrophotographic developer with silica fine powder as a charge control agent; while the No. '951 abstract illustrates a photographic developer containing a micro powder of silicate coated with alumina, and having a stable frictional charge between toner and carrier, and toner in a sleeve. In the German publication No. '635, there are disclosed toner particles and additive particles incorporated for the primary purpose of improving flowability. In the abstract of the aforementioned publication, there is mentioned as a charge control agent a metal complex dye; and further that hydrophobic colloidal silica can be selected as a flow additive. Additionally, chemically modified surface additives such as Aerosil have been disclosed in West German Patent Publication DE No. 3330380. Specifically, this publication is directed to alkoxyaminosilanes which are chemically treated with free hydroxy groups. These publications, however, do not teach the sorption of charge additives on the surface of flow aid compositions to enable the improved characteristics as illustrated hereinafter including, for example, improved admix characteristics, compatibility with various fuser rolls especially Viton fuser rolls, and the selection of low concentrations of colored dyes sorbed on the flow aid compositions preventing an adverse change in color since the dyes can be utilized in low concentrations. Further, the toner compositions of the present invention are particularly compatible with a variety of fuser rolls inclusive of Viton fuser rolls.
One Viton fuser roll selected for use in electrostatographic copying machines is comprised of a soft roll fabricated from lead oxide, and duPont Viton E-430 resin, a vinylidene fluoride hexafluoropropylene copolymer. This roll contains approximately 15 parts of lead oxide, and 100 parts of Viton E-430, which mixture is blended and cured on the roll substrate at elevated temperatures. Apparently the function of the lead oxide is to retain the liberated hydrogen fluoride gas, assist in the crosslinking reaction, contribute to degradative stability, generate unsaturation by dehydrofluorination for crosslinking, and to provide release mechanisms for the toner compositions. Excellent image quality has been obtained with Viton fuser rolls, however, in some instances there results a toner fuser compatability problem when charge control agents are part of the toner mixture. For example, it appears that certain specific charge control additives, such as quaternary ammonium compounds and alkyl pyridinium compounds, including cetyl pyridinium chloride, react with the Viton of the Viton fuser roll. For example, cetyl pyridinium chloride when part of the toner mixture appears to be catalytically decomposed by the lead oxide contained in the fuser roll resulting in a highly unsaturated compound, which polymerizes and condenses with the unsaturated Viton E-430 material. In view of this, the Viton fuser roll turns black, develops multiple surface cracks, and the surface thereof hardens thereby resulting in image quality deterioration.
Toner compositions with many of the above described charge enhancing additives are useful for causing the development of images formed on layered photoresponsive imaging devices comprised of generating layers and transport layers. These devices are charged negatively, rather than positively as is usually the situation with selenium photoreceptors, thus oa toner composition which is positively charged is required in order that the toner particles may be suitably attracted to the electrostatic latent image contained on the photoreceptor surface. Thus, efforts have been devoted to obtaining developer compositions containing toner resins which are positively charged. While many charge control additives are known for this purpose, there continues to be a need for new additives. Specifically, there continues to be a need for additives which will not interact with fuser rolls. Moreover, there continues to be a need for charge control additives which are stable at high temperatures. Also, there continues to be a need for positively or negatively charged toner and developer compositions with rapid admix charging characteristics. Further, there is a need for new charge enhancing additives, particularly those additives which can be economically prepared. Additionally, there is a need for additives which in addition to being thermally stable, are substantially nontoxic. Also, there is a need for colored toner compositions which contain positively or negatively charged resin particles, and wherein the resulting toner compositions have desirable toner admix charging. Specifically, there is a need for toner compositions having sorbed thereon modified charge enhancing additives as illustrated herein, which toner compositions can be negatively or positively charged depending, for example, on the carrier components selected; possess improved admix characteristics, that is the toner compositions acquire their charge in a rapid time period, less than 5 minutes for example; while simultaneously possessing other improved characteristics as illustrated hereinafter inclusive of acceptable electrical properties such as an appropriate positive or negative triboelectric charge.